This study aimed to investigate the effects of different doses of fresh olive pomace (FOP) application on soil chemical properties and the mineral composition of olive plant material (leaves and fruits), as well as to assess the impact on heavy metal levels in the soil. The experiment was conducted in an olive orchard at Grabovci (Croatia) during 2022 and 2023, on the domestic cv. Oblica and the introduced Italian cv. Leccino. Four fertilization treatments with pomace doses ranging from 0 to 5 kg/m² were applied. Soil analyses showed that pomace treatment significantly increased humus, phosphorus, potassium, and calcium content in the upper part of the soil, while total nitrogen was significantly elevated only at the highest dose. No increase in heavy metal concentrations in the soil was observed; in some cases, zinc, chromium, lead, and arsenic levels decreased. Fertilization with FOP positively influenced the morphological characteristics of olive fruits, increasing fruit mass, length, and width. The mineral composition of leaves and fruits exhibited optimal or elevated levels of key nutrients (N, P, K, Ca, Mg) without toxicity signs. The results confirm that FOP can be an effective organic soil amendment in olive cultivation, contributing to production sustainability and reducing the need for mineral fertilizers.
ČOGA et al. (Thu,) studied this question.